Palladium nanoparticles covered with liquid-crystalline molecules - Preparation and electro-optic properties of liquid-crystal displays doped with palladium nanoparticles

Recently an investigation was reported for improvement of a contrast ratio of liquid-crystalline matrices by addition of fullerene having a nanoscopic structure. However, this system has a disadvantage of poor miscibility of fullerene molecules in the liquid-crystalline medium. Metal nanoparticles stabilized by organic molecules are now creating a new class of materials different from either conventional bulk materials or atoms. This study aims to synthesize liquid-crystalline molecule-protected metal nanoparticles having high solubility into liquid-crystalline matrices and to develop novel display materials. 4-Cyano-4'-pentylbiphenyl (5 CB)-protected palladium (5 CB-Pd) nanoparticles with an average diameter of 1.9 nm were prepared by UV irradiation of a tetrahydrofuran solution of palladium(II) acetate in the presence of 5 CB. A guest-host liquid-crystalline device was fabricated by doping liquid-crystalline host matrices with 5 CB-Pd nanoparticles and a dichroic dye. 5 CB-Pd nanoparticles have higher solubility than fullerene into the liquid-crystalline medium. An electro-optic property in the presence of 5 CB-Pd nanoparticles is much better than that in the absence.